Automatic door bottom seals are known. A very successful automatic door bottom drop-down seal is disclosed in U.S. Pat. No. 6,125,584.
One disadvantage of the seal mechanism described in U.S. Pat. No. 6,125,584 is that downward pressure is not exerted and maintained on the seal during use to push and hold the seal against the floor. Rather, the H-shaped housing is lowered via bending of flat leaf springs which have little resistance to upward pressure.
In use the H-shaped housing drops down to rest against the floor to form a seal which may be fairly efficient in terms of a draft barrier but has little or no acoustic properties. Moreover, when a number of seal sections extend across an uneven floor, gaps between the floor and the bottom of the seal will inevitably form at various points along the length of the door.
US 2009/0077895 discloses a drop-down seal with a handle which is turned to hold the seal housing down against the floor. The use of a handle is, however, cumbersome and is undesirable to the user who generally would not wish to bend down and turn a handle located at the bottom of a drop every time the door is shut.